From a young stepmother's perspective what would you do?

My question is based mainly on being the younger stepmother. I am 19, and my husband is 31. Sadly I am 3 years older than my stepson and 6 years older than my stepdaughter (these are also my husband's stepchildren from his first marriage) my other stepchildren (his actual children)are elementary school age. We do not have any children together at the moment, but since him and his ex wife still share custody for the kids. She talks down on me due to our age difference and calls me everything in the book but a child of God. I know my stepchildren hate me because they think I'm the cause of their parents divorce, when in all actuality their marriage was broken beyond compare when I befriended him. What do I do?